Chambered Nautilus

Chambered Nautilus
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Order: Nautilida
Family: Nautilidae
Genus: Nautilus
Species: N. pompilius
Scientific name: 
  Nautilus pompilius

The Chambered Nautilus is the best-known species of nautilus. The eyes of the chambered nautilus are primitive and has no lens, thus it is comparable to a pinhole camera. The species has about 90 tentacles with no suckers. Chambered nautiluses have a pair of rhinophores, which detect chemicals in order to find their food.

Scientists have become alarmed at declining populations of nautilus resulting from overfishing, and are studying world populations to determine the need for protection under the United Nations Convention on International Trade in Endangered Species.

A live Chambered Nautilus
There are two subspecies of N. pompilius: N. p. pompilius and N. p. suluensis

N. p. pompilius is by far the most common and widespread of all nautiluses. It is sometimes called the emperor nautilus due to its large size. The distribution of N. p. pompilius covers the Andaman Sea east to Fiji and southern Japan south to the Great Barrier Reef. Exceptionally large specimens with shell diameters up to 268 mm (10.6 in)[3][4] have been recorded from Indonesia and northern Australia. This giant form was described as Nautilus repertus, but most scientists do not consider it a separate species.

N. p. suluensis is a much smaller animal, restricted to the Sulu Sea in the southwestern Philippines, after which it is named. The largest known specimen measured 160 mm in shell diameter.

The chambered nautilus is often used as an example of the golden spiral. While nautiluses show logarithmic spirals, their ratios range from about 1.24 to 1.43, with an average ratio of about 1.33 to 1. The golden spiral's ratio is 1.618. This is actually visible when the cut nautilus is inspected.

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